Some Practical Considerations in Environmental Isotope Applications in Hydrologic Studies

Research in application of environmental isotope techniques to hydrologic problems has been active and fertile over the past decade. The development of techniques for use of tritium, carbon-14 and more recently silicon-32 in groundwater dating and the broad spectrum of applications of deuterium and oxygen-18 in water problems has nearly all taken place during this period. However, the practical use of these techniques has generally not kept pace with the research and development. This is due, no doubt, in part to lack of communication between research scientists and people concerned with practical field problems, but also to the fact that water problems in the highly developed nations where the research is carried out, generally are greatly different in type and scope from water problems in the developing nations. For example, the main problems facing hydrologists in Northwestern Europe, a humid, industrialized area, are entirely different from the arid and semi-arid belts of Asia, Africa and South America. Even the most sophisticated techniques for investigating underground raters give results that are crude in comparison with the simple technique of gauging flow in a surface stream with a current meter. Likewise, quantitative estimates of interrelations of surface and underground waters are subject to similar uncertainties because underground flow of some form plays an important role in nearly all flow systems. By the same token, underground flow does not lend itself to application of simple models because of the great complexity of the flow paths. For these reasons the subsurface environment deserves the special attention of isotope workers. The task is complex and difficult but the need is great for better tools.